Low-turbidity Water Treatment Research Articles

Treatment of low-turbidity water by coagulation combining Moringa oleifera Lam and polyaluminium chloride (PAC)

A natural coagulant extracted from Moringa oleifera (MO) using saline solution (CaCl2) was associated with aluminium polychloride (PAC) for the treatment of spring water with low turbidity (10, 20 and 30 NTU) in a Dissolved Air Flotation (DAF) system. The objective was to reduce the dependence on chemical coagulants in water treatment for environmental and health reasons. Treatments at different conditions (100% MO, MO:PAC 90:10, MO:PAC 80:20, MO:PAC 70:30% and 100% PAC) were performed and analyses of turbidity, apparent colour, residual aluminium, electrical conductivity, absorbance at UV254nm and Molecular Luminescence Spectrometry (MLS) were used to determine the treatment efficiency. The use of MO alone (20, 30 and 40 mg L−1 for 10, 20 and 30 NTU waters, respectively) showed lower performance (mean removal of 66.5% for turbidity and 64.9% for colour) compared to both 100% PAC (88.3% turbidity removal and 93.1% colour removal) and MO:PAC 70:30 (79.2% turbidity removal and 90.3% colour removal). The associated coagulant did not affect the water pH. PAC dosages of 2–12 mg L−1 did not raise the residual aluminium concentration but increased the removal of compounds with absorbance at UV254nm by an average of 39.9%. Although the isolated MO exhibits poor performance in treating low-turbidity water (<30 NTU), its association with PAC is efficient, safe and sustainable, especially at a 70:30 ratio. The effect of the MO:PAC treatments in the removal of organic compounds (OC) was confirmed by MLS. The higher the proportion of PAC (30%), the lower the fluorescence intensity in the CO-predominant regions. MLS proved an excellent quality control tool to identify alterations in the configuration of organic matter in water, mainly regarding protein identification.

Selection of the Optimal Reagent for Low-Turbidity Water Treatment at High Permanganate Oxidability

The results of laboratory studies on selection of reagents and optimal dose during treatment of low-mast water of Saratov reservoir with high permanganate oxidability are presented. Laboratory studies of purification of low-yield water with high permanganate oxidability by POHA coagulants «Aqua-Aurat 30», aluminum sulfate and flocculants Praestol 650, PAA and Magnofloc LT-20 are presented, which can provide maximum degree of water clarification, with minimum content of residual aluminum in drinking water and permanganate oxidability value. The obtained results of experimental studies on the coagulation of low-flow waters of the Saratov reservoir with high permanganate oxidation in the flood period showed that the maximum decrease in permanganate oxidation concentration is achieved by settling at an optimal dose of coagulant «Aqua-Aurat 30» – 8.0 mg/dm3 by Al2O3 and a dose of flocculant Praestol 650 – 0.3 mg/dm3. The value of residual aluminium in purified water is 0.03 mg/dm3.

Basicity of titanium-based coagulants matters in the treatment of low-turbidity water

Basicity is an intrinsic factor of coagulants that plays important roles in turbidity removal. However, the effects of basicity on the coagulation performance of titanium (Ti) coagulants remain unclear. This knowledge gap is mainly due to the lack of highly polymerized Ti coagulants. In this study, we fabricated a series of Ti-based coagulants with basicity values in the range of 0–93% and evaluated their coagulation performance with simulated and real waters of low-turbidity. A positive correlation was observed between the basicity of the Ti coagulants and the coagulation performance, i.e., higher basicity led to higher turbidity removal, larger floc size, and faster settling rate. For the two titanium xerogel coagulants (TXC) of similar chemical structures, the one with a higher basicity (TXC-93%) worked better than the one of a lower basicity (TXC-78%). The advantage brought from the difference in basicity is of great significance in the purification of low-turbidity water. For the treatment of a surface river water, the required dosage of TXC-93% was about 1/2 to 1/3 of those of titanium tetrachloride (TiCl4) and polytitanium tetrachloride (PTC-21%), and was comparable to that of a high-quality commercialized polyaluminum chloride (PAC-72%). The results here provide a useful technical guidance for the mass production and application of Ti coagulants.

Performance of PATC-PDMDAAC Composite Coagulants in Low-Temperature and Low-Turbidity Water Treatment.

A novel composite was synthesized by using flocculant polyaluminum titanium silicate chloride (PATC) and poly(diallyldimethylammonium chloride) (PDMDAAC) monomers to treat low-temperature and low-turbidity water. The structure and physicochemical properties of PATC-PDMDAAC were analyzed by Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis/differential scanning calorimetry (TG/DSC), X-ray diffraction spectroscopy (XRD), and scanning electron microscopy–energy dispersion spectrum (SEM-EDS). The compound flocculant produced new functional groups exhibiting great thermal stability, and the complex chemical reaction between the two monomers generated new substances with reticular structures. Coagulation performance results showed that the PATC-PDMDAAC had an organic and inorganic ratio of 0.15 and exhibited excellent removal efficiency at pH 9.0, dosage of 1.80 mg/L, sedimentation time of 40 min, and a stirring speed of 110 r/min. The optimal treatment efficiency reduced the turbidity to 0.56 NTU (Nephelometric Turbidity Unit). The removal rates of TOC (Total Organic Carbon) and UV254 (Ultraviolet 254) were 62.18% (from 7.23 mg/L to 2.734 mg/L) and 99.99% (from 10 mg/L to 0.001 mg/L). The 3D fluorescence, zeta potential and kinetic analysis in the flocculation process indicated that coagulant electroneutralization and adsorption bridge in a slightly alkaline environment played a dominant role, and a sufficient and effective collision occurred between the coagulant and particulate matter under the optimal dosage. Lastly, PATC-PDMDAAC has more advantage than conventional flocculants in the treatment of low-temperature and low-turbidity water in the Xiangjiang River.

Preparation and Characterization of Polyaluminum Titanium Silicate and its Performance in the Treatment of Low-Turbidity Water

Using conventional coagulant, low turbidity water is difficult to achieve standard. This research uses aluminum chloride, titanium tetrachloride, and sodium silicate as raw materials for the preparation of polyaluminum titanium silicate chloride (PATC). PATC is used to treat low turbidity. The synthetic PATC showed the best coagulating effect in treated water under the following experimental conditions: Reaction temperature of 50 °C, and n(Ti)/n(Al), n(-OH)/n(Ti+Al), and n(Si)/n(Ti+Al) were 0.3, 0.2, and 1.0, respectively. The species distribution and the transformation of PATC showed that the interaction between titanium tetrachloride, sodium silicate, and the hydrolysate of Al influenced the morphology distribution of Al. Temperature and -OH greatly affected the distribution of Alb in PATC. The analysis of infrared spectra and X-ray diffraction indicated that both titanium tetrachloride and sodium silicate had complex chemical reactions with aluminum chloride. Si-O-Ti and Si-O-Al produced by the reaction affected the PATC treatment of low-turbidity water. Scanning electron microscopy showed, that compared with polyaluminum chloride(PAC), the PATC cluster was more compact, showed greater pore structure, and presented better flocculation precipitation. The optimal reaction conditions were an initial turbidity of 10 nephelometric turbidity unit(NTU), PATC dosage of 9 mg/L, pH of 8 for the simulated water sample, stirring speed of 50 r/min, and settling time of 50 min, which were determined by Orthogonal experiment. The zeta potential of the reaction process was analyzed. In the treatment of low-turbidity water, PATC mainly functioned by adsorbing, bridging, and sweeping flocculation. Electrical neutralization played an auxiliary role.

Protein fractionation of seeds of Moringa oleifera lam and its application in superficial water treatment

Abstract Moringa oleifera Lam. has been reported as a natural coagulant in the treatment of surface waters; however its use presents some disadvantages such as low performance in the coagulation/flocculation of low turbidity waters and organic matter increase in the treated water. In addition, there is little specialized literature about coagulation proteins present in Moringa seeds and their characterization. Thus, this work had as objective the fractionation of Moringa oleifera seeds protein, characterization of the fractions obtained and evaluation of potential coagulant activity in different water turbidity. Based on the results obtained it was found that the globulin and albumin presented the highest values for protein fraction in Moringa seeds with 53% and 44% respectively. Percentage removals of 87.40% of color, 89.71% of turbidity and 79.46% of UV254nm were reached using 13 mg/L of the globulin coagulant for treatment of low turbidity water (50 NTU) without entailing excessive increase of the dissolved organic carbon in the treated water, even being considered a natural coagulant. Therefore, the use of fractionation as initial purification technique proved to be beneficial by producing a coagulant with high efficiency in the treatment of the low turbidity water.

An alternative method for preparation of polyaluminum chloride coagulant using fresh aluminum hydroxide gels: Characterization and coagulation performance

The drawbacks, high energy consumption, rigorous preparation condition and high impurity contents, have been well-recognized in the preparation of widely-used polyaluminum chloride via conventional methods in industrial scale. In order to overcome the drawbacks, the fresh aluminum hydroxide gels were proposed to prepare the polyaluminum chloride (PACG) in this study. The optimal preparation condition of PACG was obtained by optimizing the preparation conditions including temperature, time and acid concentration. The contents of the small/middle polymeric aluminum (Alb) in an optimized PACG could reach 80%. During preparation, high temperature significantly reduced the preparation time but led to a poor stability. Lower rate constants of reaction between hydroxyl-Al and Ferron, kb1 and kb2, were almost equal at high basicity value. It implied that the middle polymeric aluminum (Alb2) was dominant in Alb. Besides, the pseudo-first-order kinetics equation was rearranged. Coagulation by PACG2.0 was found to be the most effective for low-turbidity water treatment but limited to a narrowest optimum range of dosage compared with other PACG. The residual aluminum concentration of the water after coagulation by the PACG2.5 with fresh aluminum hydroxide gels was always low even overdosing. Charge neutralization was not the predominant coagulation mechanism in this treatment.

Effect of Raw Water Characteristics on Sludge Reuse Process for Synthetic Low Temperature and Low Turbidity Water Treatment

Recycling ratio of mixed sludge and properties of raw water (such as pH, turbidity and organic matter concentration) were systematically investigated to optimize coagulation efficiency in current study. It was found that the appropriate recycling ratio of mixed sludge was 6%, effective initial turbidity were below 45.0 NTU, and optimal pH for dissolved organic matter and turbidity removal was 6.5-7.0 and 8.0, respectively. Residual dissolved alum (RDA) in treated water met the drinking water quality standard (&lt;0.2 mg/L). Coagulation efficiency and RDA was not negatively influenced by organic matter concentration of 1.104-3.354mgDOC/L. Under above condition, sludge reuse process could be significant for the low temperature and low turbidity water treatment.

Coagulation performance and flocs characteristics of variable sludge recycling designs for the synthetic low-turbidity water treatment

Drinking-water-precipitated sludge, characterized as accumulated suspended solids and organic or inorganic components is produced in large quantities during the coagulation process. The proper recycling of drinking water residual sludge is an effective method to enhance low-turbidity water treatment. The current research primarily focused on the settled water quality in terms of bulk parameters, i.e., fine particle distribution, turbidity, CODMn, total organic carbon, dissolved organic carbon and UV254 removal. Residual aluminum under variable sludge recycle designs was also studied. In addition, flocs characteristics was analyzed using optical microscopy and Image J software. The results indicated that recycled sludge combined with activated silica (AS) exhibited excellent potential for turbidity and particulates removal, which might be attributed to jointed effects of sweep floc, adsorption, and bridging. Moreover, powdered activated carbon (PAC) addition was significantly further improving organic matters elimination. Residual total aluminum or dissolved aluminum exceeded the requirement of drinking water treatment standard (0.2 mg/L) in China, indicating that pretreatments or subsequent treatments should be implemented or optimized to avert secondary pollution. Image analysis of regrowth flocs confirmed that recycled sludge combined with AS or/and PAC could be significant for the coagulation treatment of low-turbidity water.

Treatment of Low-Temperature and Low-Turbidity Water Using Modified Active Silica Acid

Difficult for low turbidity water treatment, the treated not reached the drinking water quality standards, the beaker coagulation has been set. In this experiment, the removal effects of low-temperature and low-turbidity water were investigated by using polyaluminum chloride (PAC) and modified active silicic acid. The results indicated that individual addition PAC turbidity removal rate was less than 80%. While adding 67 mg /L PAC and stirring 9-13min, then adding 20 ml /L modified active silica acid of 5% sodium silicate solution and 0.1% polyacrylamide solution with volume ratio of 15:1 and standing 5 min, the coagulant effect was the best and the turbidity removal rate was more than 90%. The optimizing keep time for modified active silica acid was 24 h.

Production of Natural Coagulant from Moringa Oleifera Seed for Application in Treatment of Low Turbidity Water

This study focused on developing an efficient and cost effective processing technique for Moringa oleifera seeds to produce natural coagulant for use in drinking water treatment. The produced natural coagulant can be used as an alternative to aluminum sulphate and other coagulants and used worldwide for water treatment. This study investigates processing Moringa oleifera seeds to concentrate the bio-active constituents which have coagulation activity. Moringa oleifera seeds were processed for oil extraction using electro thermal soxhlet. Isolation and purification of bio-active constituents using chromatography technique were used to determine the molecular weight of the bio-active constituents. The molecular weight of bio-active constitu-ents found to be in a low molecular weight range of between 1000 – 6500 Dalton. The proposed method to isolate and purify the bio-active constituents was the cross flow filtration method, which produced the natu-ral coagulant with very simple technique (oil extraction; salt extraction; and microfiltration through 0.45 µm). The turbidity removal was up to 96.23 % using 0.4 mg/L of processed Moringa oleifera seeds to treat low initial turbidity river water between 34-36 Nephelometric Turbidity Units (NTU) without any additives. The microfiltration method is considered to be a practical method which needs no chemicals to be added com-pared to other researchers proposed methods. The natural coagulant produced was used with low dosages to get high turbidity removal which considered to be a breakthrough in this study and recommended to be scaled up for industry level. The product is commercially valuable at the same time it is minimizing the cost of water treatment.

Coagulation pre-treatment to reduce membrane fouling in the microfiltration process of Nakdong River water

The effects of coagulation pre-treatment on microfiltration process were investigated with the Nakdong River source water. In this study, the potential membrane-fouling materials presented in the raw water were mainly attributed to particulate matters and UV254-absorbing materials. Coagulation pre-treatment mitigated the effects of these components on membrane fouling because it induced a change in the characteristics of the cake layer and a decrease in the content of UV254-absorbing materials. Even though the coagulated suspensions were not removed before MF membrane filtration, their impact on resistance to filtration was insignificant when compared with that caused by the suspensions without pre-coagulation. However, insufficient dosages of coagulant or the improper controls of coagulation pH might cause severe membrane fouling in the treatment of low turbidity water (i.e. turbidity below 10 NTU). It appeared that a selection of coagulant dosage that focused on the reduction of specific cake resistance was possibly the best way to achieve the optimal condition in this study. Also, the coagulation pre-treatment process at pH values between 5.3 and 6.8 was found to be most effective in providing the lowest specific cake resistance as well as residual UV254 absorbance.

A study on the removal of organic substances from low-turbidity and low-alkalinity water with metal-polysilicate coagulants

The coagulants of poly-aluminum-chloride (PAC), poly-aluminum-silicate-chloride (PASiC) and poly-aluminum-ferric-silicate-chloride (PAFSiC) were prepared in this study to evaluate their coagulation efficiencies and mechanisms in synthetic low-turbidity and low-alkalinity water containing organic matter. The experimental results show that PASiC and PAFSiC could remove the kaolin turbidity of the synthetic water with or without salicylic acid present. On the other hand, when the synthetic water contained both kaolin and humic acid in low turbidity and alkalinity, PAC would remove the turbidity but charge reversal of the colloidal particles would occur easily. Also, effective coagulation was limited to a very narrow dosage range. Conversely, the dosage range for the effective coagulation of both PASiC and PAFSiC was wider, although a higher dosage was required to remove the turbidity of wastewater. Therefore, the effective removal of turbidity was not only related to the kind of coagulant, but also to the types of organic matter. The coagulants PASiC and PAFSiC, particularly, proved themselves to be superior to the PAC in the treatment of low-turbidity water.

Treatment of low turbidity water by sweep coagulation using bentonite

AbstractA novel strategy of sweep coagulation to treat low turbidity water is presented herein. Study findings demonstrated that an Na+‐saturated bentonite with medium cation exchange capacity (CEC) resulted in significant turbidity removal at a bentonite dosage of 30 mg dm−3. Bentonite dispersion with fully delaminated platelets tended to undergo a more porous type of coagulation with intense face‐to‐face interactions of platelets and effectively entrapped TiO2 particles in band‐type structures. This type of coagulation usually results in a large volume of settled flocs with a fluffy structure and excellent turbidity removal efficiency for sweep coagulation. The sign and magnitude of electrical charge on TiO2 particles has a minor effect on the efficiency of sweep coagulation. Copyright © 2005 Society of Chemical Industry

Study on coagulation property of metal-polysilicate coagulants in low turbidity water treatment

In order to remove the low turbidity present in surface water, a novel metal-polysilicate coagulant was used to treat the raw water taken from Tanjiang River in Guangdong Province. This study on the effects of A1/Fe molar ratio on the performance of a complex compound formed by polysilicic acid, aluminium and ferric salt (PAFS) showed that PAFS with A1/Fe ratio of 10:3 seemed to have the best coagulation performance in removing turbidity and color. Experimental results showed that under the conditions of polymerization time of 15 d, sedimentation time of 12 min, and pH of 6-8,PAFS with A1/Fe molar ratio of 10:3 had the best coagulation efficiency and lowest residual A1 concentration. The turbidity decreased from 23.8 NTU to 3.23 NTU and the residual A1 concentration was only 0.165 mg/L in the product water. It could be speculated that colloidal impurities and particulate A1 were removed by adsorption bridging and electrical neutralization of long chain inorganic polymer coagulants.

Study on coagulation property of metal-polysilicate coagulants in low turbidity water treatment

Study on coagulation property of metal-polysilicate coagulants in low turbidity water treatment

Treatment of low-turbidity water by sweep coagulation using clay

A novel strategy of sweep coagulation to treat low-turbidity water is presented herein. Preliminary study findings demonstrate the feasibility of employing flocs formed by coagulation of montmorillonite suspension with cationic polyelectrolyte as a surrogate to the amorphous Al(OH)3 precipitated in sweep coagulation. Excellent efficiency of turbidity removal is attained via physical entrapment of TiO2 particles within the flocculating montmorillonite flocs.